Among the long-chain polyunsaturated fatty acids (LCPUFAs), and especially long-chain omega-3 fatty acids (LCn3), the fatty acids of chain length C20-C22 have received most interest in literature. The acronyms EPA (for eicosapentaenoic acid) and DHA (for docosahexaenoic acid) have become household names in describing valuable omega-3-acids from fish oil and other sources. Products rich in alpha-linoleic acid (ALA) from plant sources are also available in the market. In this regard, it is noted that lipids are described by the formula X:YnZ wherein X is the number of carbon atoms in their alkyl chain, and Y is the number of double bonds in such chain; and where “nZ” is the number of carbon atoms from the methyl end group to the first double bond. In nature the double bonds are all in the cis-form. In polyunsaturated fatty acids each double bond is separated from the next by one methylene (—CH2) group. Using this nomenclature, EPA is 20:5n3; DHA is 22:6n3 and ALA is C18:3n3. Further, as is employed herein, the term very long chain polyunsaturated fatty acids (or VLCPUFAs) is intended to mean polyunsaturated fatty acids (or PUFAs) having a chain length of more than 22 carbon atoms; the term very long chain monounsaturated fatty acids (or VLCMUFAs) is intended to mean monounsaturated fatty acids (or MUFAs) having a chain length of more than 22 carbon atoms; while the term VLCn3 is intended to refer to polyunsaturated omega-3 fatty acids having a chain length of more than 22 carbon atoms, it being understood that VLCn3 represents a sub-group of VLCPUFA.
In order to produce marine omega-3-concentrates rich in EPA and DHA, conventional industrial processes are designed to concentrate the C20-C22 fraction, by removing both short-chain fatty acids as well as larger molecules than the C22 fatty acids. Examples of such processes are molecular/short path distillation, urea fractionation, extraction and chromatographic procedures, all of which can be utilized to concentrate the C20-22 fraction of marine fatty acids and similar materials derived from other sources. A review of these procedures is provided in Breivik H (2007) Concentrates. In: Breivik H (ed) Long-Chain Omega-3 Specialty Oils. The Oily Press, PJ Barnes & Associates, Bridgwater, UK, pp 111-140.
Omega-3-acids are very liable to oxidation. In order to comply with pharmacopoeia and voluntary standards imposing upper limits for oligomeric/polymeric oxidation products, it is common to remove components with chain length above that of DHA, for example by distillation, extraction and similar procedures. Further, such higher molecular weight components of marine oils are typically associated with undesirable unsaponifiable constituents of such oil including cholesterol as well as with organic pollutants such as brominated diphenyl ethers.
However, biologically active PUFAS, including omega-3 acids are not limited to the C22 chain length of DHA. According to Poulos (Poulos A (1995) Very long chain fatty acids in higher animals—a review, Lipids 30:1-14) it is likely that VLCPUFA are normal components of most animal cells, but sensitive analytical procedures may be required to detect them in some tissues. Somewhat similarly, Poulos et al (The occurrence of polyenoic fatty acids with greater than 22 carbon atoms in mammalian spermatozoa, Biochem J. (1986) 240; 891-895) discloses that VLCPUFAs are found in a variety of mammalian spermatozoa (including human); while Rotstein et al (Synthesis of very long chain (up to 36 carbon) tetra, penta and hexaenoic fatty acids in retina, Biochem J. (1988) 249, 191-200) discloses the isolation of certain VLCPUFAs from bovine retina.
According to the American Oil Chemist's' Society's Lipid Library VLCPUFA of both the omega-3 and omega-6 families occur in the retina, brain and sperm (http://lipidlibrary.aocs.org/Lipids/fa_poly/index.htm). As recently as Nov. 20, 2014 the American Oil Chemist's' Society's Lipid Library was up-dated with a review on the metabolism of VLCPUFAs in mammals. (http://aocs.files.cmsplus.com/AnnualMeeting/images/lipidimporthtml/lipidlibrary/Lipids/fa_poly/index.htm). This review gives information that VLCPUFAs are isolated within the mammalian body to retinal tissue, testes, brain, and spermatozoa. Further, this review provides very useful information on valuable physiological roles of VLCPUFAs, including their importance for optimal functioning of the eyes and cerebral tissues as well as for male fertility. On the other hand, the review states that, unlike LCPUFAs, VLCPUFAs cannot be obtained from dietary sources, and thus must be synthesised in situ from shorter chain fatty acid precursors.
As a consequence of this belief, much work has focused upon the production of VLCPUFAs using recombinant techniques. For example, Anderson et al (US 2009/0203787A1, US 2012/0071558A1 and US 2014/0100280A1) disclose a recombinant process for producing C28-C38 VLCPUFAs using the ELOVL4 gene. Pertinently, Anderson et al indicate (in paragraph 13 of US 2009/0203787A1) that such recombinant processes are necessary as VLCPUFAs are only naturally found in extremely small quantities in a few organs or certain animal species, stating that “In order to obtain even minute μg quantities of these VLC-PUFAs, they must be extracted from natural sources such as bovine retinas. As a result, research into C28-C38 VLC-PUFAs has been limited, and means for commercial production thereof have been non-existent.”
Consequently, it is completely unexpected that certain of these VLCPUFAs could be extracted from marine oils in commercially useful amounts; including from compositions which have in the past been considered a waste product of EPA/DHA composition production processes.